Process for the production of photographic images by modifying vesicular images

ABSTRACT

Photographic images are produced by forming in a light-sensitive photographic layer a vesicular image which subsequently is transformed by treatment with a swelling agent for the binder into a stable image consisting of differences in the refractive index; the latter image can be made visible by suitable optical means.

' 22 Filed:

United States Patent {191 Weyde et al.

1 PROCESS FOR THE PRODUCTION OF PIIOTOGRAPHIC IMAGES BY MODIFY IN VESICULAR IMAGES [75] Inventors: Edith Weyde, Kurten; Maria Scheibitz; Rudolf Meyer, both of Leverkusen, all of Germany [73] Assignee: Afga-Gevaert Aktiengesellschaft,

Leverkusen, Germany Feb. 2,1972

[21] Appl. No.: 222,971 I [30] Foreign Application Priority Data Feb. 5, 1971 Germany 2105488 [52] US. Cl. 96/50 R, 96/27 R, 96/38.3, '96/48 HD, 96/60 R [51] Int. Cl G03c 5/26 8] Field of Search 96/48 R, 49, 1.1, 27 R, 96/27 E, 27 H, 38.3, 50 R, 48 HD [56] References Cited UNITED STATES PATENTS 2,911,299 11/1959 Baril et al. 94/49 3,298,833 1/1967 Gaynor I 96/27 3,316,088 4/1967 Schaffert 96/49 X June 11, 1974 3,549,376 12/1970 Roos 96/49 X 3,594,166 7/1971 Riebel'et al.... 96/27 3,615,476 10/1971 Cassiers et al. 96/49 3,615,491 10/1971 Weyde 96/48 X 3,684,511 8/1972 Weyde et a1 96/48 3,694,207 9/1972 Matejec et al 96/48 FOREIGN PATENTS OR APPLICATIONS 645,825 11/1950 Great Britain 96/91 R 402,737 3/1932 Great Britain 96/91 R OTHER PUBLICATIONS The Focal Encyclopedia, Vol. II, The Focal Press, 1965, pp, 319-320. Nieset, R. T., The Journal of Photographic Science," 1962, pp. 188-195.

Primary Examiner -Charles L. Bowers, Jr. Attorney, Agent, or Firm-Connolly and Hutz [57] ABSTRACT Photographic images are produced by forming in a light-sensitive photographic layer a vesicular image which subsequently is transformed by treatment with a swelling agent for the binder into a stable image consisting of differences in the refractive index; the latter image can be made visible by suitable optical means.

5 Claims, 3 Drawing Figures PROCESS FOR THE PRODUCTION OF PHOTOGRAPHIC IMAGES BY MODIFYING VESICULAR IMAGES v photographic images by imagewise alteration of the refractive index of the emulsion by elimination of the small bubbles of a vesicular image.

It is known to produce vesicular images by using a photographic material having a light-sensitive layer in which are dispersed compounds decomposable by light, such as diazonium salts. Upon imagewise exposure the light-sensitive compound is decomposed at the light-struck areas and a gas is evolved. Subsequent heating of the material causes the evolved gas to expand and an image formed by small bubbles is pro duced. The vesicular image thus produced causes dispersion of light at the bright-parts of the image while the unilluminated parts largely transmit light. A bubble image therefore appears dark in transmitted light but bright on viewing by' reflected light.

In Belgium Patent No. 725,903 a process for the production of photographic images is described consisting of a silver image with bubbles superimposed thereon. In this process a silver image is first produced in a hydrophilic emulsion by conventionalmethods but with a considerably lower density than the black and white images usually produced by conventional means. The emulsion is then brought into contact with a peroxide compound such as hydrogen peroxide so that at the finely-divided silver image the hydrogen peroxide is decomposed to give small bubbles of oxygen. Subsequent heating causes the bubbles to expand and a vesicular image is produced. Since the bubbles disperse light in accordance with the image, these areas appear dark when viewed by transmitted light but bright by reflected light. At the unexposed parts of the layer the impinging light is largely transmitted. Thus, a very great intensification of the silver image is achieved and, even when using silver halide emulsion layers having very little silver, deep black images with high contrast are obtained. The quality of the photographic images produced by this method is excellent.

In place of light-sensitive layers which upon exposure form nuclei of noble metal for the decomposition of hydrogen peroxide, layers can be used in the above proce'ss for the production of photographic images which contain compounds capable of forming upon exposure catalase active or peroxidase active catalysts. For example, certain complex compounds of heavy metals of groups VI b, Vllb or VIII of The Periodic Table of the elements with a monoor poly-basic carboxylic acid are suitable for this purpose. Compounds that on exposure split off iodine or iodide ions have the same effect.

For the above process light-sensitive photographic materials can also be used containing uniformly distributed, catalase active enzymes or peroxidase active ferments such as catalase, peroxidase, haemoglobin or haemin, which are deactivated on exposure to actinic light. With the said of such materials direct positive images are obtained.

The above mentioned processes yield photographic images of good quality. These images, however, have the disadvantage of inadequate stability in the presence of moisture. The gas of the bubbles which are present in the gelatine layers and which form the image, es-

capes at least partly through swelling of the layer caused by moisture so that an undesired decrease in density is observed.

It is among the objects of the invention to provide photographic processes which produce stable images of good quality.

We now have found a process for the production of photographic images by exposure of a light-sensitive layer which upon imagewise exposure from vesicles at the light-struck areas either immediately or upon processing and which vesicles are then eliminated by heating or treatment with water of the layer containing the vesicular image thus changing the refractive index of the emulsion in accordance with the image and wherein the image consisting of an alteration of the refractive index of the layer is made visible ,by suitable optical means.

The optical inhomogeneities arising on elimination of the bubble image may consist of an internal or external wrinkling of the emulsion in accordance with the im age. By external wrinkling is meant the phenomenon well known in photography in which the surface of the photographic emulsion does not stay even but is divided up by microscopically small elevations and depressions. In the case of internal wrinkling, inhomogeneities in the refractive index arise as a result of incomplete elimination of the bubble image so that some cavities remain even after prolonged treatment with swelling agents.

Light rays, on passing through an emulsion containing such inhomogeneities in the refractive index distributed in accordance with the image, will be diverted from their regular direction at these points in an irregular fashion.

If an optical device is used to screen out the rays passing regularly through the object then an image is obtained which makes visiblethe inhomogeneities in the refractive index. The parts of the image with such inhomogeneities appear light on a dark background. Two possible arrangements of this type are shown in FIGS. 1 3.

FIG. 1 shows schematically the reproduction of a schlieren transparency by the Toepler schlieren method. The optical arrangement consists of a light source 1, a condenser 2, a diaphragm 3, a lens 4 in the present case the so-called schlieren head behind which the object to be exposed 5 (schlieren object) is placed. Behind this is the screen or cut-off and an objective 6. The object reproduced on the dark background is indicated by 7.

FIG. 2 is a schematic representation of the so-called oblique illuminations method. Elements 1 6 have the same meaning as in FIG. 1. Here too the image 7 appears on the dark background.

In FIG. 3 another possibility of making visible the op tical inhomogeneities is schematically described. Here the so-called shadow projection is applied. Light from a source 1, as nearly point-like as possible, passes through a condenser 2 and a diaphragm 3 and then through the object 5. On the image screen a shadow image 8 of the object is reproduced on a bright background, unlike both the above mentioned methods. This is caused by the irregular diversion of the transmitted light at the imagewise distributed inhomogeneities in the layer; the shadow image therefore appears darker than theparts of the layer through which the light has passed regularly. The image thus appears dark on a white background. g

The vesicular images prepared as described in US. Pat. No. 3,615,491 are particularly suitable for the process of the present invention. These are based on lightsensitive silver salt emulsions, especially silver halide emulsions. Either silver chloride or silver bromide emulsions or mixtures thereof, possibly containing up to about mol percent silver iodide, are suitable. The emulsions may contain the silver halide in either fine or coarse grained form, as in the case of ammonia emulsions for example, gelatin or other natural or synthetic film formers or mixtures thereof can be used as binding agents. The photographic materials containing such emulsion layers are imagewise exposed in the usual way, developed and fixed.

The silver images thus produced are treated with a compound that is decomposed at the silver image with the formation of gaseous products. Hydrogen peroxide is expecially suitable for use as decomposable com pound. The treatment with the compound especially hydrogen peroxide, whichproduces the small bubbles can be performed in very different ways. For example, the layer of emulsion containing the developed silver image can be coated with a new layer containing hydrogen peroxide, for example with a solution .of polyvinylchloride in butanone-(2) containing hydrogen peroxide. The coating is then dried and the bubbles produced by heating. The developed photographic emulsion can also be treated with a solution of hydrogen peroxide, e.g. an alcoholic solution.

The best method is to treat the photographic emulsion with gaseous hydrogen peroxide. After about seconds exposure to asaturated hydrogen peroxide vapour the emulsion has taken up sufficient hydrogen peroxide. Of course, the time depends on the temperature and concentration of the hydrogen peroxide vapour. For example, temperature of 50 90C are suitable.

In a preferred method the developed layer of silver halide emulsion is exposed, after treatment with hydrogen peroxide vapour for about 1 5 seconds, to a steam atmosphere at about 50 4 90C. In this case, the intensifying effect, which by treatment with hydrogen peroxide alone can be brought about only relatively slowly, occurs very rapidly. 7

It is even better to expose the developed emulsion which has been treated with hydrogen peroxide to an alkaline steam atmosphere; a pH in the range of fromv 8 to 12 is suitable. This can easily be brought about by adding small amounts of ammonia or volatile amines to the steam. The concentration of the alkaline additives is not critical; in general amounts of from 0.1 to 5 percent by volume, preferably from 0.3 to 1 vol-%, have proved adequate.

The production of the visible small bubbles is brought about by expansion of the gaseous reaction products first formed. This is caused by heating to temperatures between 60 and 100C. Production of the bubbles is reinforced by slight softening of the emulsion, for example by moistening. This effect is achieved by the treatment with steam described above. This also has the effect of producing aparticularly favourable type of bubble. The bubbles are very small and the images produced from them therefore havea very high density.

'ther measures such as making the Further useful modifications of the process are described in the following US. Pat. Nos: 3,684,51 1; 3,694,207; 3,705,033 and 3,765,890.

' The images obtained by this process consist of a silver imagewith a rather low density and of a bubble image coinciding with the silver image. By treatment of the emulsions containing such images with water or steam the bubble image disappears with the onset of swelling of the emulsion. The original silver image again appears. If this film is dried, no difference can be detected, by ordinary observation, as compared with the original silver image. However, if an image such as that described is placed in the path of the rays of a suitable optical reproduction system, then the parts of the image which previously contained the bubbles and at which inhomogeneities of the refractive index are-now present, appear either dark on a white background or vice versa, according to the optical means.

The differences in the refractive index produced by the'image are irreversible, the resulting image can be stored without the need to improve the stabilityv by furimage-carrying layer water-repellent.

v was coated on to a support of polyethyleneterephthalate:

10 ml of a silver bromide gelatin emulsion containing 5 mol-% silver iodide, based on the total silver halide, and 6 percent by weight of gelatin; 260 ml of a 6 percent'aqueous solution of a photographically inert gelatin; 5 ml of a 7.5 percent by weight aqueous solution of saponin; 1.5 ml of a 30 percent formaldehyde solution, and 30 ml of an aqueous dispersion of stearyldiketene (40 percent by weight of stearyldiketene). The layer contained 0.2 g silver in the form of silver halide per m v The dried emulsion layer was imagewise exposed and developed in a developer of the following composition:

Hydroquinone p-methylaminophenol sodium sulfite 1 sodium carbonate 2 potassium bromide to 1 litre water It was then, as usual, fixed in an aqueous sodium thiosulfate bath and dried.

A negative image of the original was obtained; the maximum density was S 0.4.

The layer containing the lowdensity silver image was coatedby means of a liquid-coating roller with a solution of the following composition:

40 cm 30 percent aqueous H 0 solution cm ethanol and 2 cm glycerine.

Then the layer was run through a heating zone which dried the layer and at the same time heated the film sufficiently to yield a vesicle image with a total density of 2.0. Then the emulsion was wetted with water for long enough to make the bubble image disappear and the film was dried.

On looking at the film with an optical device as shown in FIGS. 1 or 2, the parts of the image where the bubble image was previously now appeared light on a dark background. The original silver image was notvisible by this means.

EXAMPLE 2 A light-sensitive photographic material with a layer of silver halide emulsion of the type described in Example l but which contained as a binder a mixture of gelatin and the propylene glycol ester of alginic acid in the ratio 1:1, was treated as described in the previous example. A faint silver image with a maximum density of S 0.32 was obtained. After drying briefly, the only slightly swollen emulsion was further treated as follows:

1. 30 seconds treatment with a saturated hydrogen peroxide vapour at 70C.

2. /2 second exposure to an atmosphere of water vapour at 75C.

Owing to bubble formation an extraordinarily great intensification immediately occured where the maximum density of the silver image in direct light increased to 2.1.

The bubble image was then treated with an aqueous bath and the silver image was bleached in a potassium ferricyanide toning bath, washed and dried.

In the emulsion layer thus obtained practically no image was visible. Only on viewing with one of the optical arrangements shown in FIGS. 1 and 2 an excellent white image of the original on a dark background could be observed.

EXAMPLE 3 A photographic material with a silver bromide emulsion on a cellulose acetate support, which emulsion calculated on the silver halide contained 3.5 mol-% silver iodide and the silver content of which was 0.2 g silver in the form of silver halide per qm, was imagewise exposed and developed in a developer of the following composition:

Hydroquinone p-methylaminophenol sodium sulfite sodium carbonate potassium bromide in 1 litre water It was then fixed as usual in an aqueous sodium thiosulfate bath and dried.

A negative of the original was obtained having a maximum silver density of 0.25.

In order to produce the bubble image it was coated with a peroxide paste of the following composition:

3 g polyethylene glycol with an average molecular weight of 10,000 0.2 g percarbamide (addition product of H 0 to urea l:l) 0.2 cm ethanol. The density of the emulsion was about 0.3,um. It was now heated for 30 seconds at 90C. This immediately produced the vesicular image. Now the emulsion containing the silver image and the bubble image was washed in water for 20 seconds in order to remove the bubble image.

On viewing the image by the optical method shown in FIG. 3 a black image of the original on a white background was obtained.

In general it has proved advantageous to produce the bubble image at elevated temperatures in the region of from 50 to C when the presence of small amounts of moisture has a favourable effect.

Practically any binding agent can be used for the process of the invention. Those that swell on treatment with water are particularly useful, since the bubble image can easily be eliminated. Gelatin is especially preferred as binding agent but it can be completely or partially replaced by other binders that can be swollen by water, such as alginic acid or its derivatives such as salts, amides or esters, as well as cellulose derivates, like carboxyalkylcellulose, carraghenate, starch or similar materials.

In a preferred form of the process, a mixture of gelatin and alginic acid esters, especially propylene glycol esters of alginic acid, is used because with this mixture of binders a pronounced structural change occurs on eliminating the bubble image.

We claim:

1. A process for the production of photographic images by imagewise exposure of a supported layer consisting of a water-swellable binding agent and a lightsensitive silver salt, developing the exposed layer to form a metallic silver image, treating the layer containing the silver image with a peroxide compound, heating the said layer to decompose the peroxide and to form vesicles coinciding with the silver image wherein the improvement comprises treating the vesicle containing layer in the presence of a swelling agent selected from the group consisting of water and steam for the binder to eliminate the vesicle image and produce an optical inhomogeneity coinciding with the image at those portions of the layer so that at least one portion of the layer has a refractive index that deflects light passed through the layer, and exposing the layer containing the optical inhomogeneity to light under such conditions that part of the light transmitted through the layer is distributed by the deflecting refractive index and irregularly diverted from its regular direction and forming a visible image on a screen by means of said irregularly diverted light.

2. The process of claim 1 wherein the deflected light forms the visible image by the optical schlieren method.

3. The process of claim 1 wherein the deflected light passing through the layer is made visible by the oblique illumination method.

4. The process of claim 1 wherein the deflected light passing through the layer is made visible by the shadow projection method.

5. The process of claim 1, wherein the binding agent of the silver salt emulsion layer consists wholly or in part of gelatin. 

2. The process of claim 1 wherein the deflected light forms the visible image by the optical schlieren method.
 3. The process of claim 1 wherein the deflected light passing through the layer is made visible by the oblique illumination method.
 4. The process of claim 1 wherein the deflected light passing through the layer is made visible by the shadow projection method.
 5. The process of claim 1, wherein the binding agent of the silver salt emulsion layer consists wholly or in part of gelatin. 